Boris Johnson has done "virtually nothing" to tackle rising serious youth violence, according to a former senior London government officer who drew up the Conservative mayor's initial proposals for addressing the issue.

Ron Belgrave, who left the Greater London authority (GLA) in January after six years as head of its community safety unit – the department responsible for the mayor's policies on policing and crime until a recent restructuring – has condemned the approach of Johnson's administration as "superficial, unserious and seeking to do as little as possible", while hoping the problem "would just go away".

He told the Guardian that the Tory mayoralty's commitment "seemed to end the day after the proposals were published" in November 2008, with policies failing to progress due to insufficient personnel, internal disagreements and resistance on the part of some of Johnson's key advisers on the grounds that serious youth violence was "a black issue" only.

"It was incomprehensible to me why turning the mayor's public commitment to addressing serious youth violence into reality wasn't pursued more strenuously and comprehensively. Overall, there seemed to be an uncaring and irresponsible attitude in the face of death, serious injury and widespread fear across communities in London," he said.

"It seemed that the basic attitude of the mayoralty was that addressing anything seen as a 'black issue' should be avoided wherever possible. But if a different approach had been taken from the outset who knows which deaths and injuries and what harm might have been prevented or could be in the future?"

Johnson's victory in the election of May 2008 was attributed in part to a promise to take knife crime and other violence by and against young Londoners more seriously than had his Labour predecessor, Ken Livingstone, who is seeking to regain the mayoralty at the election on 3 May.

In the latest YouGov poll, Johnson and Livingstone are almost neck and neck with the Tory candidate's lead narrowing to just two percentage points. The poll shows Johnson on 51% and Livingstone on 49% after votes for the other five candidates are stripped out. The figures come just a week after another YouGov poll gave Johnson a six-percentage point lead over his Labour rival (53%-47%).

Belgrave's intervention follows the Met commissioner Bernard Hogan-Howe's launch in February of an anti-gang-crime initiative in 19 of London's 32 boroughs in recognition of growing territory-based "postcode" violence and other crime among young people, and his admission in January that the Met's use of the stop-and-search tactics needed to be better targeted and more professional. One of Johnson's first moves on becoming mayor was to back an increase in the use of stop and search, which a report by the LSE and the Guardian cited as a factor in last August's riots.

Belgrave worked for the Labour mayor for two years. He said Livingstone had also "not done enough" on serious youth violence, yet described "an uphill battle" to turn Johnson's promises on serious youth violence into effective policies, despite a "huge outpouring of goodwill from Londoners to work together on the problem".

He said he was given just three weeks to write Johnson's initial youth policy proposals – published as a document called Time for Action – a timescale he considered "ridiculous" given that major mayoral strategies normally take about 18 months to develop, and which he says "seemed to reflect a cavalier approach to addressing the issue of young black people being killed in London".

Belgrave has also called into question the process by which a voluntary-sector partner was chosen to deliver a key strand of Time for Action, the mayor's £1.3m mentoring programme for black boys aged 10-16 thought to be at risk of drifting into crime. He has written to the GLA and to the district auditor for London, raising concerns that"there may have been malfeasance, racism and misconduct in public office" in the awarding of the funds.

The choice of a consortium led by the University of East London for the task despite a rival bid led by black-run organisations with long mentoring experience – twice achieving the highest scores for its interviews and presentations to a "decision panel", which Belgrave was on – has been controversial in the black voluntary sector.

Belgrave, who described himself as "the latest in a series of black senior officers to have been restructured out of City Hall since 2008", said work on developing a proper strategy for identifying the roots and reducing the incidence of serious youth violence was impeded by the attitude of a number of Johnson's advisers.

He claims that some of those given responsibility for implementing elements of the Time for Action programme actively opposed tailoring measures to address the statistical over-representation of black boys as both perpetrators and victims of violent crime.

He also said Kit Malthouse, the Tory London assembly member who heads the newly created mayor's office for policing and crime and previously chaired its predecessor, the Metropolitan Police Authority, was "overly focused on enforcement" and had no appetite for "driving the SYV [serious youth violence] agenda with the approach, level of priority and importance it required".

Belgrave said no permanent team of GLA officers had been formed under Johnson to address serious youth violence until May 2010 – two years after his election – despite an opportunity presented by a restructuring of the GLA bureaucracy in spring 2009.

Belgrave's criticisms are in keeping with those made by three of the six members of an unpaid panel of youth violence experts – the mayor's expert advisory group (MEAG) – personally put together by Johnson in July 2010 in response to concerns that Time for Action was failing to resonate among black Londoners.

The former MEAG member Gus John, an educationalist who ran youth services for the old Inner London Education Authority, last month described the mayor's strategy to the Guardian as "directionless" and "a shambles", and Malthouse and Johnson's then chief-of-staff Sir Simon Milton (who died in April 2011) as "dinosaurs" and "very dismissive" of ideas for engaging community support.

John said there was confusion and conflict from the start about the MEAG's role and queried the transparency of criteria by which people were deemed eligible to join it. He said the MEAG "lacked credibility, purpose, integrity, everything" and resigned from it in December 2010. "I didn't want to give it any credibility by being associated with it," he said.

In his letter to Johnson explaining his decision, he wrote: "From the outside, the continued operation of the group in its current form looks like a cynical exercise of going through the motions."

Another MEAG member, the leadership coach Viv Ahmun, described the months of his involvement as "a very painful period because there was so much resistance to what we were doing". He says he believes the group's efforts were "sabotaged behind the scenes" by influential members of the mayor's team.

Richard Taylor, the father of Damilola Taylor, who was killed aged 10 by two older boys in south London in November 2000, was also a MEAG member. The Damilola Taylor Trust told the Guardian that Taylor was "hugely frustrated" by his experience with Johnson's city hall.

The MEAG produced a report for the mayor in January 2011 that contrasted failures of "top-down" public-sector provision with emerging research showing that community-based, "bottom-up" interventions could help to diagnose and address the issue. It listed educational underachievement and the psychological impact of stop and search on innocent young black people among issues for attention, and described as "essential" a programme to better understand the roots of youth violence and identify effective interventions.

Belgrave said resources had been available to undertake such work but that the report was "immediately shelved" and the role of MEAG members thereafter restricted to what he calls "tokenistic" appearances at a series of public meetings – "community conversations". The group has now ceased to exist.

A source close to the mayor told the Guardian that, "Boris Johnson ended an era of appalling complacency on youth crime, bringing energy, imagination and total commitment to seeking solutions. His comprehensive strategy – Time for Action – was a top priority from day one and led to innovative and unprecedented projects.

"He consulted experts in the field regularly and embarked on the most intense programme of engagement with the black community ever attempted by city hall through his community conversations. Though frustrated by the pace of delivery, his commitment remains absolute."